When I traded for my Romanian WASR AK47, the other guy told me that the spring (called a "shepherd's crook by some people) that hols the trigger and hammer springs was broken. That would allow the retaining pins for those items to fall out.
So, I went to midway and found just what I needed-an AK retaining plate, made by Tapco, number AK0690. It took just a few minutes to install it. Now, I have a fully operational AK with no worry about losing the trigger or hammer pins.
The cost was $5, so, I ordered 2. The shipping was the same for either one or two, so I decided to have a spare. I think that everybody who has an AK should have an extra one of these as well as a few other parts such as springs. You just never know.